In recent years, with an increase in the population of aged people, the number of aged patients having senile cataract has noticeably increased. The cataract is a disease in which a lens is opacified, and it induces a decrease in the vision and may sometimes deprive a patient of his or her eyesight. For treating a patient with cataract, the opaque lens and cortex are removed and the vision is corrected with an ophthalmic lens or a contact lens, or an intraocular lens is inserted. It is a generally practiced method at present to remove the lens and then fix an intraocular lens in the capsule.
In the above method, however, remaining lens epithelial cells migrate into the posterior lens capsule and proliferate to generate opacification in the posterior capsule region, and the opacification may spread over the optic portion of the intraocular lens and may cause secondary cataract. For treating this secondary cataract after the insertion of an intraocular lens, there is employed a method in which the opacified portion is removed by irradiation with an Nd:YAG laser beam. However, this method has defects that the apparatus therefor is expensive and that the fundus examination, photocoagulation and vitreous body operation are hampered (for example, see NISHI Okihiro, et al., “Secondary Cataract Inhibiting Effect of Intraocular Lens”, Summary of the 15th Europe Intraocular Lens Society Conference, 1997).
As other method, there are known a method of treating and preventing secondary cataract by using a medicine (for example, see JP-A-9-291040), a method of forming an intraocular lens whose circumferential portion has sharp edges to inhibit the secondary cataract (for example, see the above Summary of the 15th Europe Intraocular Lens Society Conference) and a method of coating that portion of an intraocular lens which corresponds to the posterior capsule portion with a biocompatible material having a specific composition (for example, see Japanese Translation Version No. 2002-511315 of PCT Application).
Meanwhile, the entire surface of the anterior capsule portion is incised in the surgery for inserting a lens, and the lens front surface inserted is hence exposed to aqueous humor, etc., unlike the lens back surface side. In recent years, it has come to known that the opacification phenomenon also occurs on the lens front surface side.
There has been so far no intraocular lens that not only inhibits secondary cataract but also works to inhibit the opacification phenomenon that occurs on the lens front surface side.